This invention relates to a bit addressable linear modulator and, more particularly, to a modulator comprised of plural arrays of controllable reflecting fingers and an optical system therefor.
An extended Total Internal Reflection (TIR) light modulator/scanner of the type shown in U.S. Pat. No. 4,281,904 to R. A. Sprague et al is a single integrated device which images all the picture elements of a recording line simultaneously onto a photoreceptor. In that system, a polarized laser beam is focused at a relatively large TIR modulator, and is modulated by a spatially varying phase pattern generated by applying a voltage pattern to an array of individually addressed electrodes driven by an LSI chip. A Schlieren optical system with a zero-order stop is used to image the phase pattern onto the photoreceptor utilizing the central dark ground method.
However, the very nature of this type of imaging system may present problems. For example, a relatively large TIR modulator is required and this leads to reduction in fabrication yields. Coupling of the electric field into the electro optic crystal of the modulator may be degraded due to the small gap between the metal electrodes and the crystal. There may also be problems in providing a suitable soft interface.
Further, the optical system suffers from the common problem of non-uniformity in light across the recording line due to Gaussian fall-off of the laser beam and the possibility of dark areas (i.e. intensity nulls) between adjacent picture elements found with the central dark ground imaging method. And, the use of a Schlieren optical system in applications of this type may create a need for delicate optical alignment procedures which normally must be performed at the factory using special equipment rather than in the field.